Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.10.3.2 (laccase)
4,656 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Laccase is one of the ligninolytic enzymes found in liquid cultures of the fungus Ceriporiopsis subvermispora in defined medium. As an approach to a clarification of the role of laccases during the attack on lignin by the fungus, the enzyme has been characterized further. The levels of this phenol oxidase increase 2-fold in the presence of p-anisidine and are severely affected when addition of either Mn(II) or Cu(II) ions to the medium is omitted. Isoelectrofocusing allowed the resolution of two laccase isoenzymes, with pIs of 3.65 and 3.59. In rich medium, laccase activity is 10-fold higher than in salt medium, and it is not affected by the external addition of p-anisidine or Mn(II). Four isoenzymes were detected in these cultures, with pIs between 3.76 and 3.60. In a wheat bran medium, four isoenzymes with pIs in the range 3.63-3.46, plus a fifth isoenzyme of high pI (4.82), were also identified. The absorption spectrum of a pool containing the four isoenzymes from rich medium shows a maximum at 600 nm, typical of laccase possessing a type I copper atom. The molecular mass of the isoenzyme with pI 3.60 is 79 kDa, as determined by SDS/PAGE. Upon treatment with endoglycosidase F, the molecular mass of this isoform decreases to 63 kDa, indicating a high degree of glycosylation. Substrate specificity studies conducted with the four isoenzymes from rich medium and a combination of isoenzymes from salt medium showed marked differences among them. The amino-terminal sequences (24 residues) of three isoenzymes isolated from rich medium were determined. Two of them are identical, whereas the third one differs from these in three amino acid residues. The consensus sequence reveals clear homology with laccases from other microorganisms.
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PMID:Properties of laccase isoenzymes produced by the basidiomycete Ceriporiopsis subvermispora. 779 34

Penicillin X methyl ester was transformed into three types of dimer by laccase from Coriolus versicolor. The dimers are considered to be formed by free-radical addition of phenoxy radicals produced by laccase. The enzyme reaction with the ester as substrate was more suitable for forming dimers than that with the sodium salt as substrate. Penicillin X pivaloyloxymethyl ester was also transformed into a dimer, which had antibacterial activity in the presence of esterase.
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PMID:Enzymatic dimerization of penicillin X. 843 47

A laccase (EC 1.10.3.2) was isolated from the culture filtrate of Lentinula edodes. The enzyme was purified to a homogeneous preparation using hydrophobic, anion-exchange, and size-exclusion chromatographies. SDS-PAGE analysis showed the purified laccase, Lcc 1, to be a monomeric protein of 72.2 kDa. The enzyme had an isoelectric point of around pH 3.0. The optimum pH for enzyme activity was around 4.0, and it was most active at 40 degrees C and stable up to 35 degrees C. The enzyme contained 23.8% carbohydrate and some copper atoms. The enzyme oxidized 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, p-phenylendiamine, pyrogallol, guaiacol, 2,6-dimethoxyphenol, catechol, and ferulic acid, but not veratryl alcohol, tyrosine, and beta-(3,4-dihydroxyphenyl) alanine. The N-terminal amino acid sequence of Lcc 1 showed close homology to the N-terminal sequences determined for laccases from Phlebia radiata, Trametes villosa, and Trametes versicolor, but only low similarity was observed to a previously reported laccase from L. edodes. Lcc 1 was effective in the decolorization of chemically different dyes - Remazole Brilliant Blue R, Bromophenol Blue, methyl red, and Naphtol Blue Black - without any mediators, but the decolorization of two dyes - red poly(vinylamine)sulfonate-anthrapyridone dye and Reactive Orange 16 - did require some redox mediators.
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PMID:Purification and characterization of an extracellular laccase from the edible mushroom Lentinula edodes, and decolorization of chemically different dyes. 1243 15

Chlorinated phenols are major industrial and agricultural xenobiotics that pollute soil and ground water. It has been shown that laccases catalyze the oxidative coupling of phenolic compounds. Therefore, the transformation of one or a mixture of several chlorinated phenols by a laccase from the fungus Trametes villosa was studied. Generally, if more than one phenol was added, the transformation of chlorinated phenols decreased, and if the concentration of the laccase was increased, the transformation of the phenols was enhanced. There were exceptions to these observations: for instance, the transformation of 0.1 mM 4-chlorophenol incubated with 1 mM 2,4-dichlorophenol in buffered salt solutions was not enhanced if the concentration of the laccase was increased from 2 to 20 DMP units/mL. The reason for the reduced transformation of chlorinated phenols in the presence of additional phenols is still unknown. However, in spite of some limitations, the application of laccase to decontaminate wastewater polluted with chlorinated phenols appears feasible.
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PMID:Enzymatic oxidative transformation of chlorophenol mixtures. 1254 43

The diversity of ascomycete laccase sequences was surveyed in a southeastern US salt marsh using a degenerate primer set designed around copper binding sites conserved in fungal laccases. This gene was targeted for diversity analysis because of its potential function in lignin degradation in the salt marsh ecosystem and because few studies have assessed functional gene diversity in natural fungal communities. Laccase sequences were amplified from genomic DNA extracted from 24 isolates (representing 10 ascomycete species) cultured from decaying blades of Spartina alterniflora, and from DNA extracted directly from the decaying blades. Among the ascomycete isolates, 21 yielded a PCR product of expected size (900 bp) that was tentatively identified as laccase based on sequence similarities to previously published laccase sequences from related organisms. Overall, 13 distinct sequence types, containing 39 distinct sequences, were identified among the isolates, with several species yielding multiple distinct laccase types. PCR amplifications from early and late decay blades of S. alterniflora yielded seven laccase types. Of these, five were composed of sequences >96% similar at the amino acid level to sequences from three cultured ascomycetes previously found to be dominant members of the fungal communities on decaying S. alterniflora blades. Two of the laccase types from the natural-decay clone library were novel and did not match any of the sequences obtained from the cultured ascomycetes. The 39 distinct sequences and 15 distinct laccase sequence types retrieved from the S. alterniflora decay system demonstrate high sequence diversity of this functional gene in a natural fungal community.
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PMID:Diversity of ascomycete laccase gene sequences in a southeastern US salt marsh. 1263 11

A laccase (EC 1.10.3.2) was isolated from the fully browned gills of Lentinula edodes fruit bodies. The enzyme was purified to a homogeneous preparation using hydrophobic, cation-exchange and size-exclusion chromatography. SDS-PAGE analysis showed the purified laccase, Lcc 2, to be a monomeric protein of 58.0 kDa. The enzyme had an isoelectric point of around pH 6.9. The optimum pH for enzyme activity was around 3.0 against 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS), and it was most active at 40 degrees C and stable up to 50 degrees C. The enzyme contained 8.6 % carbohydrate and some copper atoms. The enzyme oxidized ABTS, p-phenylenediamine, pyrogallol, guaiacol, 2,6-dimethoxyphenol, catechol and ferulic acid, but not veratryl alcohol and tyrosine. Beta-(3,4-dihydroxyphenyl)alanine (L-DOPA), which was not oxidized by a laccase previously reported from the culture filtrate of L. edodes, was also oxidized by Lcc 2, and the oxidative product of L-dopa was identified as L-DOPA quinone by HPLC analysis. Lcc 2 was able to oxidize phenolic compounds extracted from fresh gills to brown-coloured products, suggesting a role for laccase in melanin synthesis in this strain.
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PMID:Important role of fungal intracellular laccase for melanin synthesis: purification and characterization of an intracellular laccase from Lentinula edodes fruit bodies. 1294 71

The white-rot fungus Daedalea quercina produced the ligninolytic enzymes laccase and Mn-dependent peroxidase. Laccase was purified using anionexchange and size-exclusion chromatographies. SDS-PAGE showed the purified laccase to be a monomeric protein of 69 kDa (71 kDa using gel filtration) with an isoelectric point near 3.0. The optimum pH for activity was below 2.0 for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (K(m)=38 microM), 4.0 for 2,6-dimethoxyphenol (K(m)=48 microM), 4.5 for guaiacol (K(m)=93 microM) and 7.0 for syringaldazine (K(m)=131 microM). The temperature optimum was between 60 and 70 degrees C depending on the pH and buffer used. The enzyme was stable up to 45 degrees C, and stability was higher at alkaline pH. Enzyme activity was increased by the addition of Cu(2+) and inhibited by Mn(2+), sodium azide, dithiothreitol, and cysteine. Laccase from Daedalea quercina was able to decolorize the synthetic dyes Chicago sky blue, poly B-411, remazol brilliant blue R, trypan blue and reactive blue 2.
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PMID:Purification and characterization of laccase from the white-rot fungus Daedalea quercina and decolorization of synthetic dyes by the enzyme. 1450 38

Effects of humic acid on removal of hydroxy polychlorobiphenyls (PCBs) with laccase from Trametes versicolor were studied. In the absence of humic acid, hydroxy PCBs were rapidly degraded by laccase. However, the rate constants decreased with increasing humic acid concentration, the reactions being completely inhibited at 150 mg l(-1) of humic acid. Peroxidase from Arthromyces ramosus was not inhibited by the same treatment. The activity of humic acid-deactivated laccase was completely restored by copper ions (500 microM of Cu2+ in 150 mg l(-1) of humic acid), but not by other metal ions (Zn2+, Fe2+ and Hg2+). Humic acid-deactivated laccase purified by gel permeation chromatography (GPC) showed no activity against 2,2'-azino-bis(3-ethylbenzthiazoline sulfonic acid) diammonium salt and 3,5-dichloro-4-hydroxybiphenyl, but its activity was restored by copper ion treatment. Humic acid-deactivated laccase showed similar properties, such as GPC retention time and copper ion requirements for activity, to those of laccase deactivated by nitrilotriacetic acid. The extent of humic acid inhibition, expressed as activity non-recoverable by copper ion treatment, increased over time more rapidly than that of the humic acid-free control. These results suggest that short-term inactivation of laccase, i.e., less than 1 day, is attributable to a depletion of copper ion.
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PMID:Copper dissociation as a mechanism of fungal laccase denaturation by humic acid. 1456 87

Hydroxy polychlorinated biphenyls (hydroxy PCBs) are toxic metabolites of PCBs. Their toxicity such as strong endocrine disruption demands effective remediation methods. Laccases from Trametes versicolor and Pleurotus ostreatus were tested to degrade hydroxy PCBs. Optimum pHs for both enzymes were around 4.0. Laccase from T. versicolor degrades hydroxy PCBs more rapidly than that from P. ostreatus. The enzymatic activities remained little changes in up to 10% organic solvents, but decreased rapidly in more than 10% acetone, acetonitrile or DMSO. Degradation rate constants decreased with increase of chlorination and no degradation was observed with tetra-, penta- and hexa-chloro hydroxy PCBs in non-mediated reactions. However, the tetra- to hexa-chloro hydroxy PCBs were degraded by laccase from T. versicolor in the presence of the mediator 2,2,6,6-tetramethylpiperidine-N-oxy radical. The other mediators, 4-ethyl-2-methoxyphenol, 2,2'-azino-bis(3-ethylbenzthiazoline sulfonic acid) diammonium salt and 1-hydroxybenzotriazole and humic acid, also enhanced degradation of all the hydroxy PCBs except 4-hydroxy-2',3,3',4',5,5'-hexachlorobiphenyl. The results showed that 3-hydroxy biphenyl was more resistant to laccase degradation than 2- or 4-hydroxy analogues. Significant linear-correlations (coefficient of determination, r2 = 0.9097 and 0.8186 for laccases from P. ostreatus and T. versicolor, respectively) were found between the ionization potentials and the removal rate constants of hydroxy PCBs.
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PMID:Fungal laccase-catalyzed degradation of hydroxy polychlorinated biphenyls. 1510 76

Characterisation of the aminoxyl (>N-O*) radical BTNO, generated from 1-hydroxybenzotriazole (HBT) by the one-electron oxidant CAN (a Ce(IV) salt), confirms BTNO as the reactive intermediate in oxidations run with the laccase/HBT system.
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PMID:Spectrophotometric, EPR and kinetic characterisation of the >N-O* radical from 1-hydroxybenzotriazole, a key reactive species in mediated enzymatic oxidations. 1549 18


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